Oxalate-bridged dirhenium(I) hexacarbonyl complexes: synthesis, reactions, and crystal structures

Formation of “A-frame” dirhenium(I) hexacarbonyl complexes by trans-1,2-bis(diphenylphosphino)ethylene and bis(bidentate) ligands

“…The C^O stretching patterns of complexes 1e4 are very similar to that of [Re 2 (m-dppene)(CO) 6 (m,h 2 :h 2 -C 2 O 4 )] [4]. As expected, thẽ n max of [Re 2 (m-dppene)(CO) 6 (m,h 2 :h 2 -C 2 O 4 )] (2033 cm À1 ) is much higher than that of its tetrathiooxalate analogue, 2 (2018 cm À1 ).…”

“…2.467 Å for the chelated diphosphine complex, [13]. The ReeP bonds of [Re 2 (m-dppene)(CO) 6 (m,h 2 :h 2 -C 2 O 4 )] (average 2.502 Å) are similarly elongated [4].…”

“…Complex 1 was prepared in a similar way as its oxalate analogue, [Re 2 (m-dppene)(CO) 6 (m,h 2 :h 2 -C 2 O 4 )] [4]. The precursor,…”

“…Surprisingly, the major product (79% yield) of the reaction was [Re 2 (m-dppene)(CO) 6 (m,h 2 :h 2 -C 2 O 4 )], which has an "Aframe" structure with a syn-bridging dppene (Fig. 1) [4]. This structure, with almost perfectly eclipsed ReeP bonds (ReeP/PeRe torsional angle of 0.7 ) and a rather short Re/Re distance (5. The facile formation of [Re 2 (m-dppene)(CO) 6 (m,h 2 :h 2 -C 2 O 4 )] and its stability raised the possibility of preparing analogous complexes, wherein the oxalate ligand is replaced by 1,2-dithioooxalate (dto), tetrathiooxalate (tto), dithiooxamidate (dtox) or oxamidate (oxa) (Scheme 1).…”

Rhenium carbonyl complexes with monodentate-coordinated diphosphines: activation of terminal phosphino groups towards amine-oxide oxidation

“…Mechanism 2 requires the diphosphine to adopt a chelating conformation in transition-state B, which would not be possible for dppene. Mechanism 1, on the other hand, requires the diphosphine to adopt an A-frame-like conformation, which is possible for dppene [6]. Hence, if Mechanism 2 is correct, no phosphine-oxide complex would be observed for dppene.…”